It is sometimes desirable to commingle or hybridize two or more continuous multiple filament yarns into a single yarn to provide the combined beneficial characteristics of the two different materials in a single yarn. Such commingled yarns make possible the manufacture of advanced thermoplastic composite parts in very complex shapes. For example, commingled carbon and polyether ether ketone (PEEK) yarns are desirable, because, in a mold under heat and pressure, the PEEK melts and flows around the carbon fibers, forming a lightweight, reinforced plastic without the complications of the more traditional wet epoxy and polyester resin systems.
Curzio U.S. Pat. No. 4,539,249 discloses combining graphite fibers from one spool with thermoplastic resin fibers from other spools by passing thermoplastic and graphite fibers through a guide plate, twisting these fibers and overwrapping these fibers with additional resin fibers from additional spools to provide a blended yarn.